This paper presents some evidence of a positive effect of Agriculture R&D investment on economic growth in general dynamic setting using annual data for 57 developing countries for the period 1981-2010. The potential endogeneity of Research and Development Investment is also addressed to identify causal effect using GMM Style internal instrument that successfully pass various validity tests. Our analysis separates the growth effect and the level effect of R&D investment. The result appears to be robust to various proxies for Agriculture R&D investment. The finding suggests the intensification of investment in research and development in developing countries to boost agricultural productivity and economic growth.